First insights on phytohormones during the compatible grapevine-phylloxera interaction

Phylloxeration on grapevines demands the formation of a gall to initiate and sustain a complex, specialized and intimate host-parasite interaction. The galls (histoid leaf galls, root nodosities or tuberosities) are characterized by altered gene expression and highly active metabolism supplying the parasite with nutrients. In this study we analysed the endogenous regulation and role of stress-related hormones in plant-defence in galls to understand the physiological crosstalk and metabolism of the compatible phylloxera grapevine root interaction. Concentrations of main phytohormones were quantified on nodosities from Teleki 5C (V. riparia × V. berlandieri) combined with a phylloxera single founder lineage biotype C. Our results suggest pivotal and positive role of cytokinins for root gall formation whereas the auxin homeostasis was downregulated in infested nodosities. We conclude that phylloxera is able to impose specific changes in hormone pools, thus modulating hormone-based defence in strict dependence on their parasitism stage.